I bought ear muff water flusher for my Suzuki 20 HP 4 stroke and attached it to the water intake vavles. I made sure the vavles were completely covered and made sure water was flowing though the motor flusher. The outboard was in neutral and when I cranked the outboard to turn it on, I did not see any water flowing our of the pisser valve. I hit the kill switch because I was worried I would overheat the engine. Any ideas of what is going wrong?

Check your impeller. I was constantly replacing the one on my 15hp zuke. It would melt inside the housing and then disintegrate. I started flushing the motor by submerging it in a cooler and the problem was solved.